MFL36414401

CAUTIONBEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

Website http://biz.lgservice.com

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MICROWAVE OVENSERVICE MANUALMODEL: MH-1446SQP

삼 흥정 판

P/NO : MFL36414401October, 2006

Printed in Korea

This device is to be serviced only by properly qualified service personnel.Consult the service manual for proper service procedures to assure continued safety operation and for precautions to betaken to avoid possible exposure to excessive microwave energy.

PRECAUTIONS TO BE OBSERVED BEFORE ANDDURING SERVICING TO AVOID POSSIBLEEXPOSURE TO EXCESSIVE MICROWAVE ENERGYA) Do not operate or allow the oven to be operated with the door open.

B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other

microwave source, and make repairs as necessary; (1)interlock operation, (2)proper door closing, (3)

seal and sealing surfaces (arcing, wear, and other damage), (4)damage to or loosening of hinges and

latches, (5)evidence of dropping or abuse.

C) Before turning on microwave power for any service test or inspection within the microwave generating

compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,

integrity, and connections.

D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation

and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual

before the oven is released to the owner.

E) A microwave leakage check to verify compliance with the Federal Performance Standard should be

performed on each oven prior to release to the owner.

SAFETY PRECAUTIONS

CAUTIONMICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOROR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

(Page)

SAFETY PRECAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Inside front cover

SPECIFICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1-1

CAUTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-1

INSTALLATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3-1

OPERATING INSTRUCTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1

FEATURES - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1

CONTROL PANEL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1

OPERATING SEQUENCE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-2

SCHEMATIC DIAGRAM - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-3

CIRCUIT DESCRIPTION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-4

SERVICE INFORMATION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1

TOOLS AND MEASURING INSTRUMENTS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1

MICROWAVE LEAKAGE TEST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-1

MEASUREMENT OF MICROWAVE POWER OUTPUT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-3

DISASSEMBLY AND ADJUSTMENT - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-3

INTERLOCK CONTINUITY TEST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-7

COMPONENT TEST PROCEDURE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-8

TROUBLE SHOOTING - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5-12

EXPLODED VIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6-1

REPLACEMENT PARTS LIST - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7-1

CONTENTS

1-1

SPECIFICATIONS

This microwave oven is designed for household use only.

It is not recommended for commercial purposes.

DESCRIPTION

MH-1446SQP

120 Volts AC 60 HzMicrowave 1400WGrill 1200WSingle phase, 3 wire grounded

1000 Watts full microwave power (IEC60705)

2450 MHz

2M246 - 050GF

0 ~ 99 min. 99 sec

556 (W) x 320 (H) x 405 (D) (mm)

398 (W) x 247 (H) x 396 (D) (mm)

16.5 kg (approx.)

18.5 kg (approx.)

Touch Control System

Clock : 1:00 - 12:59

Microwave Power for Variable Cooking

Power level

HIGH ............................... Full power throughout the cooking time

9 (Saute) .......................... approx. 90% of Full power, 8 (Reheat) .......approx. 80%

7 (Med.-High) .................. approx. 70%, 6 (Medium) ......approx. 60%

5 (Med.-Low) ................... approx. 50%, 4 (Defrost) .......approx. 40%

3 (Low) ............................ approx. 30%, 2 (Simmer).......approx. 20%

1 (Warm) ......................... approx. 10%

Owner's manual

Glass turntable

Roller rest

Grill rack

ITEM

MODEL

Power Requirement

Power Output

Microwave Frequency

Magnetron

Timer

Outside Dimensions

Cavity Dimensions

Net Weight

Shipping weight

Control Complement

Rating Label Location

Accessories

Back Side

• DO NOT operate on a 2-wire extension cord duringrepair and use.

• NEVER TOUCH any oven components or wiring duringoperation.

• BEFORE TOUCHING any parts of the oven, alwaysremove the power plug from the outlet.

• For about 30 seconds after the oven stops, an electriccharge remains in the high voltage capacitor. Whenreplacing or checking, you must discharge the highvoltage capacitor by shorting across the two terminalswith an insulated screwdriver.

• Remove your watches whenever working close to orreplacing the Magnetron.

• DO NOT touch any parts of the control panel circuit. Aresulting static electric discharge may damage thisP.C.B.

• NEVER operate the oven with no load.• NEVER injure the door seal and front plate of the oven

cavity.• NEVER put iron tools on the magnetron.• NEVER put anything into the latch hole and the

interlock switches area.

• Proper operation of the microwave oven requires thatthe magnetron be assembled to the waveguide andcavity. Never operate the magnetron unless it isproperly installed.

• Be sure that the magnetron gasket is properlyinstalled around the dome of the tube wheneverinstalling the magnetron.

2-1

CAUTIONS

Unlike other appliances, the microwave oven ishigh-voltage and high-current equipment.Though it is free from danger in ordinary use,extreme care should be taken during repair.

THE OVEN IS TO BE SERVICED ONLYBY PROPERLY QUALIFIED SERVICEPERSONNEL.

MICROWAVE RADIATIONPersonnel should not be exposed to themicrowave energy which may radiate from themagnetron or other microwave generatingdevice if it is improperly used or connection.All input and output microwave connections,waveguide, flange and gasket must be securenever operate the device without a microwaveenergy absorbing load attached.Never look into an open waveguide or antennawhile the device is energized.

GasketANTENNA

COOLING FIN

MAGNETRONCHASSIS GROUND

FILAMENTTERMINALS

MAGNETRON

3-1

INSTALLATIONS

INSTALLING1. Empty the microwave oven and clean inside it with

a soft, damp cloth. Check for damage such asmisaligned door, damage around the door or dentsinside the cavity or on the exterior.

2. Put the oven on a counter, table, or shelf that isstrong enough to hold the oven and the food andutensils you put in it. (The control panel side of theoven is the heavy side. Use care when handling.)

3. Do not block the vent and the air intake openings.Blocking vent or air intake openings can causedamage to the oven and poor cooking results.Make sure the microwave oven legs are in place toensure proper air flow.

4. The oven should not be installed in any area whereheat and steam are generated, because they maydamage the electronic or mechanical parts of theunit.Do not install the oven next to a conventionalsurface unit or above a conventional wall oven.

5. Use microwave oven in an ambient temperatureless than 104°F (40°C).

6. Place the microwave oven on a sturdy and flatsurface at least 10 cm (4 inches) from the wall.

7. Place the microwave oven as far away as possiblefrom TV, RADIO, COMPUTER, etc., to preventinterference.

GROUNDING INSTRUCTIONSFor personal safety, this appliance must be fullygrounded at all times.

In the event of an electrical short circuit, groundingreduces the risk of electrical shock.The plug must be plugged into an outlet that isproperly installed and grounded.

BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.

10cm

WARNINGImproper use of the grounding plug can result in arisk of electric shock.Do not, under any circumstances, cut or remove thethird ground prong from the power cord plug.

PREFERRED METHOD

ENSURE PROPER GROUNDEXISTS BEFORE USE

TEMPORARY METHOD(ADAPTER PLUGS NOTPERMITTED IN CANADA)

ALIGN LARGEPRONGS/SLOTS

ENSURE PROPER GROUNDAND FIRM CONNECTIONBEFORE USE

4-1

OPERATING INSTRUCTIONS

FEATURES

CONTROL PANEL 1. INDICATORS

2. LATIN MENU

3. OPTION

4. NUMBER: Used to set for time of day, cooking time,power level or defrost weight.

5. AUTO DEFROST: Used to select the desired autoweight defrost programmed with weight pad.

6. Q-DEFROST

7. MICRO: Used to cook food for a desired time.

8. COMBI: Used to cook food by microwave andcombination.

9. GRILL: Used to cook food by microwave and grill.

10. HOLD WARM

11. POWER: Used to select power level for cooking.

12. CLOCK: Used to set the time of day.

13. STOP/CLEAR: Used to stop oven and clear allentries except time of day.

14. START/ADD 30 SECOND: One tap allows oven tobegin functioning.

Roller Rest

Grill Rack

1

2

4

14

5

8

10 3

11

12

13

6

79

4-2

OPERATING SEQUENCEThe following is a description of component functionsduring oven operation.

1. SETTING THE CLOCK

ex.) To set 4:30, touch number key [4],[3], and [0].NOTE: 1) This is a 12 hour clock.

2) Clock will operate as long as power isapplied to the oven.

2. CANCEL FUNCTIONTouch the pad whenever you need tocancel an entry or a function currently in use.The display will either return to the last item enteredor to the clock.

3. ADD 30 SECOND

4. LATIN MENU

NOTE: Heat only 1 package at a time

5. TIME COOKING

6. MULTI-STAGE COOKING

1ST STAGE

2ND STAGE

7. AUTO WEIGHT DEFROST COOKING

8. CHILD LOCKThis oven has a CHILD LOCK feature• TO SET CHILD LOCK• Touch the pad• Touch and hold PARAR/BORRAR pad LOCK

appear on the display.

• TO CANCEL CHILD LOCK• Touch the pad• Touch and hold PARAR/BORRAR pad LOCK

disappears.

9. GRILL COOKING

10. COMBI COOKING

PARAR/BORRAR RELOJ RELOJNUMBER

Más 30 Seg.PARAR/BORRAR

PARAR/BORRAR TIME POTENCIANUMBER

NUMBER INICIO

PARAR/BORRAR TIME POTENCIANUMBER

NUMBER

PARAR/BORRAR

TIME POTENCIANUMBER

NUMBER INICIO

PARAR/BORRAR AUTO DESCONGPOR PESO NUMBERNUMBER OF

WEIGHT

PARAR/BORRAR

PARAR/BORRAR

PARAR/BORRAR DORADOR INICIO

Desiredcooking

time

PARAR/BORRAR COMBI INICIO

Desiredcooking

time

FRIJOLES NUMBER INICIOPAUSA/BORRAR

SCHEMATIC DIAGRAM

4-3

4-4

CIRCUIT DESCRIPTIONGENERAL DETAILS • The low voltage transformer supplies the necessary

voltage to the micom controller when power cord isplugged in.

• When the door is closed, the primary switch is ON, thesecondary switch is ON, and the monitor switch opens(contact COM and NO).

WHEN SELECTING COOKING POWERLEVEL AND TIME• The micom controller memorizes the function you set.• The time you set appears in the display window.• Each indicator light turns on to indicate that the stage

has been set.

WHEN TOUCHING THE START PAD• The coil of the relay is energized by the micom

controller.• Power input is supplied to the high voltage transformer

through the fuse to the primary switch and relay 2.• Turntable rotates.

• The fan motor rotates and cools the magnetron byblowing the air (coming from the intake on thebaseplate).

• The air is also directed into the oven to exhaust thevapor in the oven through the upper plate.

• Cooking time starts counting down.• 3.2 volts AC is generated from the filament winding of

the high voltage transformer. This 3.2 volts is applied tothe magnetron to heat the magnetron filament throughtwo noise-preventing choke coils.

• A high voltage of approximately 2100 volts AC isgenerated in the secondary of the high voltagetransformer which is increased by the action of the highvoltage diode and charging of the high voltagecapacitor.

• The negative 4000 Volts DC is applied to the filamentof the magnetron.

WHEN THE OVEN IS SET AT ANY LEVELEXCEPT MAXIMUM.• The micom controller controls the ON-OFF time of relay

2 by the applied signal to vary the average output

power of microwave oven as POWER LEVEL.(refer to page 1-1)

WHEN THE DOOR IS OPENED DURINGCOOKING• Both the primary switch and relay 2 are cut off primary

winding voltage of the high voltage transformer.• ON-OFF of relay 2 is coupled electrically with opening

and closing of the secondary switch.• When the door is opened, the secondary switch is

opened and when the door is closed, the secondaryswitch is closed.

• The cooking time stops counting down.• Relay stops functioning.• As the door is opened, if the contact of primary switch

and relay 2 and/or secondary switch fails to open, thefuse opens due to the large current surge caused bythe monitor switch activation, which in turn stopsmagnetron oscillation.

WHEN TOUCHING THE START KEYWITH THE GRILL COOKING FUNCTIONSELECTED• The contacts of the primary switch and the secondary

switch close the circuit.• A.C. voltage is applied to the grill heater through grill

thermostat as shown by the solid line.• Turntable rotates.

• The fan motor rotates.• The air is also directed into the oven to exhaust the

vapor in the oven through the base plate and upperplate.

L

FUSE

H.V.TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARYSWITCH

PRIMARYSWITCH

N

MONITORSWITCH

MONITORSWITCH

L

FUSE

H.V.TRANS-

FORMER

RELAY 2

MICOM CONTROLLER

SECONDARYSWITCH

PRIMARYSWITCH

N

RELAY 3

L

N

OVENTHERMOSTAT

GRILL HEATER

L

G -Y

N

E

5-1

NECESSARY TOOLSTools normally used for TV servicing are sufficient.Standard tools are listed below.

• Diagonal pliers• Long nose pliers• Phillips screwdriver• Flat blade screwdriver• Wrench (size 5mm)• Nutdriver (size 5mm)• Adjustable wrench• Soldering iron• Solder• Vinyl insulation tape• Polishing cloth

CAUTIONS• Be sure to check microwave leakage prior to

servicing the oven if the oven is operative prior toservicing.

• The service personnel should inform themanufacture importer, or assembler of any certifiedoven unit found to have a microwave emissionlevel in excess of 5 mW/cm2 and should repair anyunit found to have excessive emission levels at no costto the owner and should ascertain the cause of theexcessive leakage. The service personnel shouldinstruct the owner not to use the unit until the oven hasbeen brought into compliance.

• If the oven operates with the door open, the servicepersonnel should:- Tell the user not to operate the oven.- Contact the manufacturer and CDRH(Center for Devices and Radiological Health)immediately.

NOTE: Address on CDRHOffice of Compliance(HFZ-312)Center for Devices and RadiologicalHealthe 1390, Piccard Drive,Rockville. MD 20850

• The service personnel should check all surface andvent openings for microwave leakage.

• Check for microwave leakage after every servicing. Thepower density of the microwave radiation leakageemitted by the microwave oven should not exceed 4 mW/cm2. Always start measuring of an unknown fieldto assure safety for operating personnel from radiationleakage.

NECESSARY MEASURING INSTRUMENTS• TESTER (VOLTS-DC, AC, Ohmmeter)• Microwave survey meter- Holaday HI-1500

HI-1501- Narda 8100

8200• Inch scale• 600 cc non conductive material beaker (glass or plastic),

inside diameter: approx. 8.5 cm(31/2 in.)• Cylindrical and made of borosilicate glass vessel.

max. thickness: 3 mmoutside diameter: approx. 190mmheight: approx. 90mm

• Glass thermometer: 100°C or 212°F (1 deg scale)

MEASURING MICROWAVE ENERGYLEAKAGE• Pour 275±15 cc of 20±5°C(68±9°F) water in a beaker

which is graduated to 600 cc, and place the beakeron the center of the turntable.

• Set the energy leakage monitor to 2450 MHz anduse it following the manufacturer's recommendedtest procedure to assure correct result.

• When measuring the leakage, always use the 2- inch(5 cm) spacer supplied with the probe.

• Operate the oven at its maximum output.• Measure the microwave radiation using and

electromagnetic radiation monitor by holding theprobe perpendicular to the surface being measured

Move probe along shaded area

Probe scanning speedLess than 2.5 cm/sec(1 in/sec)

SERVICE INFORMATIONTOOLS AND MEASURING INSTRUMENTS

MICROWAVE LEAKAGE TEST

MEASUREMENT WITH OUTER CASEREMOVED• When you replace the magnetron, measure for

microwave energy leakage before the outer case isinstalled and after all necessary components arereplaced or adjusted.Special care should be taken in measuring thefollowing parts. (Circled area of Fig. below)- Around the magnetron- The waveguide

MEASUREMENT WITH A FULLYASSEMBLED OVEN• After all components, including the outer case, are fully

assembled, measure for microwave energy leakagearound the door viewing window, the exhaust opening,and air inlet openings.

• Microwave energy leakage must not exceed the valuesprescribed below.

NOTE: Leakage with the outer case removed less than5 mW/cm.sq. Leakage for a fully assembledoven (Before the latch switch (primary) isinterrupted) with the door in a slightly openedposition-less than 2 mW/cm.sq.

NOTES WHEN MEASURING• Do not exceed meter full scale deflection.• The test probe must be removed no faster than

1 inch/sec (2.5 cm/sec) along the shaded area,otherwise a false reading may result.

• The test probe must be held with the grip portion of thehandle.A false reading may result if the operator's hand isbetween the handle and the probe.

• When testing near a corner of the door, keep the probeperpendicular to the surface making sure the probe ismoved horizontally along the oven surface.

RECORD KEEPING AND NOTIFICATIONAFTER MEASUREMENT• After adjustment and repair of any microwave energy

interruption or microwave energy blocking device,record the measured values for future reference. Alsoenter the information on the service invoice.

• The microwave energy leakage should not be morethan 4 mW/cm.sq. after determining that all parts are ingood condition, functioning properly and genuinereplacement parts which are listed in this manual havebeen used.

• At least once a year, have the electromagnetic energyleakage monitor checked for calibration by itsmanufacturer.

WARNING : AVOID CONTACTING ANYHIGH VOLTAGE PARTS

5-2

5-3

• Microwave power output measurement is made withthe microwave oven supplied at its rated voltage andoperated at its maximum microwave power setting witha load of (1000 ± 5)g of potable water.

• The water is contained in a cylindrical borosilicate glassvessel having a maximum material thickness of 3 mmand an outside diameter of approximately 190 mm.

• The oven and the empty vessel are at ambienttemperature prior to the start of the test.

• The initial temperature (T1) of the water is (10±2)°C. Itis measured immediately before the water is added tothe vessel. After addition of the water to the vessel,the load is immediately placed on the center of theturntable which is in the lowest position and themicrowave power switched on.

• The time T for the temperature of the water to rise by avalue ∆T of (10±2)°K is measured, where T is the timein seconds and ∆T is the temperature rise. The initialand final water temperatures are selected so that themaximum difference between the final watertemperature and the ambient temperature is 5°K.

• The microwave power output P in watts is calculatedfrom the following formula:

4187 x (∆T) + 0.55 X (T2 - T0)X M

T• T2 : Temperature after heating• T0 : Temperature after bowl• M : Weight of bowl

is measured while the microwave generator isoperating at full power. Magnetron filament heat-uptime is not included. (about 3 sec)

• The water is stirred to equalize temperature throughoutthe vessel, prior to measuring the final watertemperature.

• Stirring devices and measuring instruments are selectedin order to minimize addition or removal of heat.

WATER LOAD

TURNTABLE

MEASUREMENT OF MICROWAVE POWER OUTPUT

P =

DISASSEMBLY AND ADJUSTMENTA. OUTER CASE REMOVAL1) Disconnect the power supply cord from the outlet.2) Remove the screws from the rear of the case.

The outer case must be moved backward to be liftedoff.

B. POWER SUPPLY CORD1) Remove the outer case.2) Disconnect two terminals and remove one screw of

the ground terminal.

C. CONTROL PANEL ASSEMBLY1) Open the door.2) Disconnect the leadwire from RELAY (RY2) of the

PCB SUB ASSEMBLY.2) Disconnect the leadwire from connector (CN1) of the

PCB SUB ASSEMBLY.3) Lift up and pull out control panel assembly carefully

from the cavity.

CAUTION: DISCHARGE THE HIGH VOLTAGECAPACITOR BEFORE SERVICING(refer to page 2-1)

Remove the screw

Lift up and pull out control panel

5-4

D. PCB ASSEMBLY REMOVAL1) Remove the control panel assembly from the

cavity. (Refer to control panel assembly removalon previous page.)

2) Remove screws which hold the PCB SUBASSEMBLY to the control panel.

3) Disconnect the flat cable from the PCB SUBASSEMBLY and take off the PCB SUB ASSEMBLY.

E. DOOR ASSEMBLY / REMOVAL1) Open the door.2) Remove the choke cover very carefully with a flat-blade

screwdriver.CAUTION: Be careful not to damage door seal plate

by screwdriver.3) Lift up and push the door.

NOTE:1. After replacing the door, be sure to check that the

primary switch, monitor switch, and secondary switchoperate normally.

2. After replacing the door, check for microwave energyleakage with a survey meter. Microwave energy mustbe below the limit of 4 mW/cm2. (with a 275 ml waterload)

3. When mounting the door assembly to the ovenassembly, be sure to adjust the door assembly parallelto the chassis. Also, adjust so the door has no playbetween the inner door surface and oven frameassembly. If the door assembly is not mountedproperly, microwaves may leak from the clearancebetween the door and the oven.

Remove choke cover

Remove door assembly

Spacer

5-5

F. MAGNETRON REMOVAL1) Disconnect the leadwire from the magnetron.2) Carefully remove the mounting screws holding the

magnetron and the waveguide.3) Remove the magnetron ASSEMBLY until the tube

is clear from the waveguide.

NOTE:1. When removing the magnetron, make sure its

dome does not hit any adjacent parts, or it may bedamaged.

2. When replacing the magnetron, be sure to installthe magnetron gasket in the correct position andbe sure that the gasket is in good condition.

3. After replacing the magnetron, check for microwaveleakage with a survey meter around themagnetron. Microwave energy must be below thelimit of 5 mW/cm2. (With a 275 ml. water load).Make sure that gasket is rigidly attached to themagnetron. To prevent microwave leakage,tighten the mounting screws properly, making surethere is no gap between the waveguide and themagnetron.

G. REMOVING THE TURNTABLE MOTOR1) Remove the turntable and rotating ring.2) Lay the unit down on its back.3) Remove the turntable motor cover.

The turntable base cover is easily removed bypinching the eight parts with a wire cutting.

4) Disconnect the leadwire from the turntable motorterminals.

5) Remove the screw securing the turntable motor tothe oven cavity ASSEMBLY.

6) After repairing the motor, rotate the removedturntable motor cover.

7) Fit the turntable motor cover’s projecting part to thebase plate slit.

NOTE:1. Remove the wire lead from the turntable motor

VERY CAREFULLY.2. Be sure to grasp the connector, not the wires, when

removing.

H. HIGH VOLTAGE TRANSFORMERREMOVAL

1) Discharge the high voltage capacitor.2) Disconnect the leadwire from magnetron, high voltage

transformer, and capacitor.3) Remove the screw holding the high voltage

transformer to the baseplate.

I. FAN MOTOR ASSEMBLY / REMOVAL1) Discharge the high voltage capacitor.2) Disconnect the leadwire from fan motor and high

voltage capacitor.3) Remove the two screws holding the the suction guide

ASSEMBLY to the oven cavity.4) Remove the two screws holding the fan motor

ASSEMBLY to the suction guide ASSEMBLY.

J. HIGH VOLTAGE CAPACITOR ANDDIODE REMOVAL

1) Discharge the high voltage capacitor.2) Disconnect the leadwire from fan motor and high

voltage capacitor.3) Remove the screw holding the suction guide

ASSEMBLY to the oven cavity.4) Remove the screw holding the high voltage capacitor

bracket and remove the high voltage diode earthscrew.

K. INTERLOCK SYSTEM1) INTERLOCK MECHANISM

The door lock mechanism is a device which hasbeen specially designed to eliminate microwaveactivity when the door is opened during cooking andthus to prevent the danger resulting from themicrowave leakage.

2) MOUNTING OF THE PRIMARY/MONITOR/SECONDARY SWITCHES TO THE LATCHBOARD

3) INSTALLATION AND ADJUSTMENT OF THELATCH BOARD TO THE OVEN ASSEMBLY

• Mount the latch board to the oven assembly.• Adjust the latch board in the arrow direction so that

oven door will not have any play in it when the dooris closed.

• Tighten the mounting screw.• Check for play in the door by pushing the door

release button. Door movement should be lessthan 0.5 mm. (1/64 inch)Don't push the door release button while making thisadjustment. Make sure that the latch moves smoothly after adjustment is completed and that thescrews are tight. Make sure the primary, monitor,and secondary switches operate properly byfollowing the continuity test procedure.

5-6

PRIMARYSWITCH

MONITORSWITCH

SECONDARYSWITCH

ADJUSTMENTDIRECTION

A. PRIMARY INTERLOCK SWITCH TESTWhen the door release button is depressed slowlywith the door closed, an audible click should beheard at the same time or successively atintervals. When the button is released slowly, thelatches should activate the switches with anaudible click.If the latches do not activate the switches whenthe door is closed, the switches should be aadjusted in accordance with the adjustmentprocedure. Disconnect the wire lead from theprimary switch. Connect the ohmmeter leads tothe common (COM) and normally open (NO)terminal of the switch. The meter should indicatean open circuit in the door open condition. When the door is closed, the meter shouldindicate a closed circuit.When the primary switch operation is abnormal,make the necessary adjustment or replace theswitch only with the same type of switch.

B. SECONDARY INTERLOCK SWITCH TESTDisconnect the wire lead from the secondaryswitch.Connect the ohmmeter leads to the common(COM) and normally open (NO) terminals of theswitch. The meter should indicate a open circuit inthe door open condition. When the door is closed,meter should indicate an closed circuit. When thesecondary switch operation is abnormal, make thenecessary adjustment or replace the switch onlywith the same type of switch.

C. MONITOR SWITCH TESTDisconnect the wire lead from the monitor switch.Connect the ohmmeter leads to the common(COM) and normally closed (NC) terminals of theswitch. The meter should indicate closed circuit inthe door open condition. When the door is closed,meter should indicate an open circuit. When themonitor switch operation is abnormal, replace withthe same type of switch.NOTE: After repairing the door or the interlocksystem, it is necessary to do this continuitytest before operating the oven.

INTERLOCK CONTINUITY TEST

5-7

WARNING : FOR CONTINUED PROTECTION AGAINST EXCESSIVE RADIATIONEMISSION, REPLACE ONLY WITH IDENTICAL REPLACEMENT PARTS.

TYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR PRIMARY SWITCHTYPE NO. SZM-V 16-FA-62 OR VP-532A-OF FOR MONITOR SWITCHTYPE NO. SZM-V 16-FA-63 OR VP-533A-OF FOR SECONDARY SWITCH

COMPONENTS TEST PROCEDURE RESULTS

SWITCHES Check for continuity of the Door Door(Wire leads removed) switch with an Ohm-meter open closed

PrimarySwitch

MonitorSwitch

NOTE : After checking for the continuity of switches, make sure that they areconnected correctly.

NOCOM

NC

COM

NOCOM

SecondarySwitch

5-8

CAUTIONS1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE

OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGHVOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THEHIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1)

2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1 LITEROF WATER IN CONTAINER) IN THE OVEN.

COMPONENTS TEST PROCEDURE RESULTSHIGH VOLTAGETRANSFORMER(Wire leads removed)

MAGNETRON(Wire leads removed)

1. Measure the resistance.(Ohm-meter scale: Rx1 and Rx100)• Primary winding• Secondary winding• Filament winding

2. Measure the resistance.(Ohm-meter scale: Rx1000)• Primary winding to ground• Filament winding to ground

1. Measure the resistance. (Ohm-meter scale: Rx1)• Filament terminal

2. Measure the resistance.(Ohm-meter scale: Rx1000)• Filament to chassis

Approx.: 0.2 ~ 0.4 ohmApprox.: 60 ~ 90 ohmLess than: 1 ohm

Normal: InfiniteNormal: Infinite

Normal: Less than 1 ohm

Normal: Infinite

COMPONENT TEST PROCEDURE

5-9


HIGH VOLTAGECAPACITOR

HIGH VOLTAGEDIODE

NOTE :Some inexpensive metersmay indicate infiniteresistance in both direction.

Measure the resistance.(Ohm-meter scale: Rx1000)• Terminal to terminal.

Measure the resistance.(Ohm-meter scale: Rx1000)• Terminal to case.

Measure the continuity (Forward).(Ohm-meter scale: Rx10000)

Measure the continuity (Reverse).(Ohm-meter scale: Rx10000)

Normal: Momentarily indicatesseveral ohms, andthen gradually returnsto infinite.

Normal: Infinite.

Normal: Continuity.Abnormal: Infinite.

Normal: Infinite.Abnormal: Continuity.

NOTE: When testing the magnetron, be sure to install the magnetron gasketin the correct position and be sure that the gasket is in good condition.

Antenna

Gasket

Chassis

Filament

5-10


HEATER ELEMENT(Wire leads removed.)

THERMOSTAT

FUSE(Wire leads removed.)

Measure the resistance.(Multi-meter scale:RX1)

Measure the resistance with 500V-100MOhm insulation resistance meter.

Check the continuity of the switchwith an Multi-meter

Normal:Gill heaterApprox.15 Ω(at 20-30oC)

Normal:more than 1.0M Ω

NOTE: Make sure heater is fully cooled when tested.

NOTE: If the fuse is blown, check primary, the secondary, the monitorswitches, H.V.D and H.V.C before replacing the fuse.If the fuse is blown by improper switch operation replace the defectiveswitch and the fuse at the same time.Replace just the fuse if the switches operate normally.

0°C~Approx 110°C Over 180°C

Normal Abnormal


5-11

RELAY 2

FAN MOTOR(Wire leads removed)

TURNTABLEMOTOR(Wire leads removed)

Normal:A: Approx. 85 ~ 100 ohm.B: Approx. 10 ~ 25 ohm.

Abnormal: Infinite or severalohms.

Normal: Approx.100~150 ohmAbnormal: Infinite or several

ohm.

NOTE : • A MICROWAVE LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT ISSERVICED FOR ANY REASON.

• MAKE SURE THE WIRE LEADS ARE IN THE CORRECT POSITION.• WHEN REMOVING THE WIRE LEADS FROM THE PARTS, BE SURE TO GRASP THE

CONNECTOR, NOT THE WIRES.

POWERLEVEL

12345678910

4 sec6 sec8 sec10 sec12 sec14 sec16 sec18 sec20 sec22 sec

18 sec16 sec14 sec12 sec10 sec8 sec6 sec4 sec2 sec0 sec

Relay 2

A

B

Measure the resistance.(Ohm-meter scale: R x 1)

Check for continuity of relay 2 with anohm-meter.(Remove wire leads from relay 2 andoperate the unit.)

Measure the resistance.(Ohm-meter scale: R x 1)

5-12

TROUBLE SHOOTING

WHEN YOU GET A COMPLAINT FROM YOUR CUSTOMER, EVALUATE THE COMPLAINT CAREFULLY. IFTHE FOLLOWING SYMPTOMS APPLY, PLEASE INSTRUCT THE CUSTOMER IN THE PROPER USE OF THEMICROWAVE OVEN. THIS CAN ELIMINATE AN UNNECESSARY SERVICE CALL.

CAUTIONS1. Check grounding before checking for trouble.2. Be careful of the high voltage circuit.3. Discharge the high voltage capacitor. (See page 2-1)4. When checking the continuity of the switches or of the high voltage transformer, disconnect one lead wire

from these parts and then check continuity with the AC plug removed. To do otherwise may result in afalse reading or damage to your meter.

5. Do not touch any part of the circuit on the PCB since static electric discharge may damage this controlpanel.Always touch yourself to ground while working on this panel to discharge any static charge built up in yourbody. (Micom model only)

CONDITION

Microwave ovendoes not work.

Inserting many plugs into oneoutlet and using them at thesame time.(blown fuse or breaker)

Microwave oven plug is notinserted tightly.

Output power is too low. Low AC input voltage.

Food temperature is too low.

Using metallic ware andallowing it to touch the ovenwall.

Sparks occur.

Inconsistent intensity ofmicrowave by theircharacteristics.

1. Use plastic wrap or lid.2. Stir once or twice while

cooking soup, cocoa ormilk, etc.

Uneven cooking.

Ceramic ware trimmed ingold or silver power is used.

Avoid using other electricalappliances when you use themicrowave oven.

Insert microwave oven plugsecurely.

Use the microwave oven atadequate line voltage.

This may not be a defect.It is possible that the foodshould be cooked for alonger time period.

Do not use metallic ware forcooking except that noted inthe cooking guide.

Do not use any type ofcookware with metallictrimming.

CAUSE REMEDY

1. Incomplete segments.• Segment missing.• Partial segment missing.• Digit flickering (NOTE: Slight flickering is normal.)

2. Colon does not turn on or blink.3. A distinct change in the brightness of one or more numbers in display.4. One or more digits in the display are not lighting.5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.6. Specific numbers (for example 7 or 9) will not display when key pad is touched.7. Display does not count down with time blinking or up with clock operation.8. Display obviously jumps in time while counting down.9. Display counts down too fast while cooking.

10. Each indicator light does not turn on after setting cooking cycle.11. Display time of day does not reappear when cooking is finished.

5-13

(TROUBLE 1) The following visual conditions indicate a probable defective control circuit.

CONDITION CHECK RESULT CAUSE REMEDY

Everything worksas specified.

Continuity.

No continuity.

Still have trouble.

Defective keymembraneassembly.

Defective PCBassembly.

Looseconnection.


Replace keymembraneassembly.

Replace PCBassembly.

Connect themtightly.


Replace keymembraneassembly andcheck operation.

Check the conn-ection betweenmembrane keyassembly andPCB assembly.

2. Some inputscannot beprogrammed.

1. No input can beprogrammed.

3. Display shows anumber or figuredifferent from onetouched.

4. Randomprogrammingwhen touchingother pads.

5. Display is fixedat some figureand can notaccept anyinput.

5-14

(TROUBLE 2) Oven does not operate at all; Display window does not display any figures,and no input is accepted.

NOTE : All these switches must be replaced at the same time. Refer to page 5-7, 5-8

2. Fuse does notblow.

No continuity.

No continuity.Replace powersupply cord.

Defectivethermostat.

Defective powersupply cord.

Replacethermostat.

Check continuityof thermostat.

Check continuityof power supplycord.

Continuity.


1. Fuse blows. Continuity.

No continuity.

Continuity. Shorted contact atthe primary switch.

Replace fuse,primary, monitorsecondaryswitches, andRELAY(RY2) ofP.C.B Assembly.

No continuity.

Normal.Defective highvoltage capacitor.

Replace highvoltage capacitor.

Fuse blows againDefective high volt-age transformer.

Replace high volt-age transformer.

Malfunction of themonitor switch.

Replace fuse,primary, monitorsecondaryswitches, andRELAY(RY2) ofP.C.B Assembly.

Check continuityof monitorswitch (withdoor closed).

Check continuityof primaryswitch (withdoor opened).

Disconnect oneside of the wirelead connectedfrom transformerto the highvoltagecapacitor andoperate the unit.

Replace fuse

Continuity. Malfunction ofsecondary switch.

Replace fuse,primary, monitor,secondaryswitches, andRELAY(RY2) ofP.C.B Assembly.

No continuity.

Check continuityof secondaryswitch (withdoor opened).

5-15

(TROUBLE 3) Display shows all figures set, but oven does not start cooking while desiredprogram times are set and START pad is touched.

(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.


1.Setting timedoes not countdown whentouching STARTpad.

2. Fan motor oroven lamp donot turn on.

No continuity.

Continuity.

Continuity

No continuity

Check the con-nection betweenCN1 connectorand PCBassembly.

Defectivesecondary switch.

Replacesecondary switch.



Check continuityof secondaryswitch (withdoor closed).

Check fan motor.

Check oven lamp.

Abnormal

Abnormal

Normal

Defective fan motor.

Defective oven lamp.

Replace fan motor.

Replace oven lamp.

Loose connection.Connect themtightly.


Output is low.Lower than 90% ofrating voltage.

Normal.

Normal.

Abnormal.

Abnormal.Measure theoutput power.

Disconnect thewire leads fromrelay 2 andcheck on and offtime withmultitester.



Decrease in powersource voltagewith load.

Suggest customercontact localelectric powerutility companyor qualifiedelectrician.

Check thepower sourcevoltage.

Defectivemagnetron.

Replacemagnetron.

NOTE: Simple test of power output-conducted by heating one liter water for one min. if available.Minimum 8.5˚C temperature rise is normal condition.

5-16

(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.(Display operates properly)


No microwaveoscillation.

No continuity.

Continuity.



Disconnect thewire leads fromrelay 2 andcheck continuityof relay 2.(Operate the unit)

Normal

Normal

AbnormalDefective highvoltage capacitor.

Replace highvoltage capacitor.

Check high vol-tage capacitor.

Abnormal Defective highvoltagetransformer.

Replace highvoltagetransformer.

Check high vol-tage transformer.

AbnormalDefective highvoltage diode.

Replace highvoltage diode.

Check high vol-tage diode.

Normal

AbnormalDefectivemagnetron.

Replacemagnetron.

Checkmagnetron.

5-17


Output is full whenyou set lowerpower level.

Abnormal.Defective P.C.B.assembly.

Replace P.C.B.assembly.

Disconnect thewire leads fromrelay 2 and checkcontinuity relay 2.(Operate the unit)

(TROUBLE 6) Oven does not cook properly when programmed for the set power level(Operates properly on HIGH)

(TROUBLE 7) Grill


1. Heater is notoperating.

Abnormal.

Normal.

Normal.

Heater.

Thermostat andrelay3.(Grill)

Abnormal.Malfunction thethermostat.

Malfunction theheater.

Replace.

Wire connection. No continuity. Open or loosen.Replace orconnect tightly.

Replace.

1. Lower tempera-ture the oven.

Abnormal.

Normal.

Heater.

Thermostat andrelay3.(Grill)

Abnormal.Malfunction thethermostat.

Malfunction theheater.

Replace.

Replace.

NOTE : • Make sure the wire leads are in the correct position.• When removing the wire leads from the parts, be sure to grasp the connector, not the wires.• When removing the magnetron, be sure to install the magnetron gasket in the correct position

and in good condition.

6-1

EXPLODED VIEW

INTRODUCTIONMODEL: MH-1446SQP

#EV#

6-2

13213A

13552A

15006A

13581A13536A

14026A

14970A

13720D

14890A

DOOR PARTS

#EV#

6-3

23572A

24781M

WTP018

268711

24510L

250201

24970A

23506A

CONTROL PANEL PARTS

#EV#

6-4

35889A

33052M

36549S 35300A

33390G

35026G

33112U

44360A

WTP013

WNH001

348101

348101

WTT021

WTT010

348102

WTP004

34980A

OVEN CAVITY PARTS

#EV#

6-5

43501A

WSZ085

466001

466001

466003

43500A

LATCH BOARD PARTS

#EV#

6-6

568771

WSZ002

WSZ002

WSZ002

WSZ002

WEB001

WTT028

56411A

56930V

56549F

54974S

WTT037

55900A

54810C

WTT028

50CZZH

34930W

56912B

55262A

948501

56324A56851D

WEB001

50FZZA

56201A

35012A

INTERIOR PARTS

#EV#

6-7

WTT021

63302A

63303A

56170D

WSZ002

948502

65006B

BASE PLATE PARTS

#EV#